1. Field of the Invention
The present invention relates to a flat image display device having a fluorescent material as a light-emitting material, such as a field emission display device (FED) and a plasma display device (PDP). More particularly, the present invention relates to a fluorescent material and a fluorescent substrate for use in a flat image display device.
2. Description of the Related Art
In a flat image display device such as FED and PDP, an image is displayed by energizing a fluorescent material. Therefore, fluorescent materials with a high luminance have to be used in such flat image display devices.
However, the luminance of the fluorescent material can be degraded in the process of manufacturing the flat image display device having the fluorescent material. The luminance of the fluorescent material can also degrade in a long-term use of the image display device after the image device has been manufactured.
Accordingly, a configuration has been suggested in which a coating layer including SiO2 as the main component is formed on the surface of fluorescent particles and the fluorescent particles are protected (Japanese Patent Laid-Open No. 2002-338959).